The principle of an electrolytic apparatus is well known. Such an apparatus includes cells containing an electrolyte and equipped with electrodes. Under the effect of an electrical field established between the electrodes the ions move in the direction of this field towards the said electrodes. The cations move towards the cathode and the anions move towards the anode. When the ions arrive at the electrodes they abandon to them their electrical charge and are transformed into neutral atoms. In the case of the electrolysis of water the electrolyte is water to which potash has generally been added. The reactions at the electrodes lead to the formation of hydrogen at the cathode and oxygen at the anode. Each cathode is separated from the opposite anode by a diaphragm. The water consumed must be replaced. So electrolyte is brought through feed channels at the bottom of the cells. The oxygen gas and the hydrogen gas which are produced at the electrodes are collected at the upper part of the cells.
Various types of apparatus are known which serve for the electrolysis of water. Generally two neighboring electrode plates are separated by at least one annular frame which forms with the said electrode plates one cell containing electrolyte. This cell is divided by the diaphragm into two compartments of which one contains the anolyte and the other the catholyte. The apparatus, because it is provided with a set of electrode plates, includes a stack of frames which are clamped between two clamping plates subjected to a clamping system. Each compartment includes in the upper part an orifice enabling gas to be collected and in the lower part an inlet enabling the introduction of the electrolyte. In certain apparatus each electrode is anodic on one side and cathodic on the other. These electrodes are called bipolar.
Certain bipolar apparatus operate at high temperature and pressure. This operation under pressure procures a better output.
Flow of the electrolyte must be prevented through the joint planes which are formed by the generally plane annular faces of the frames. Such flow would have the consequence of causing corrosion phenomena and pressure differences between the anodic and cathodic compartments. The sealing must be controlled when the operational pressure is high.